Curing of copolymers



Patented Apr. 19, 1949 UNITED STATES PATENT OFFICE CURING OF COPOLYMEBS Raymond E. Harris, Stamford, Conn., assignor to American Cyanamid Company, New York, N. Y., a corporation of Maine N Drawing. Application October 10, 1944, Serial N0. 558,086

Claims. (Cl. 260-454) This invention relates to the activation of catalysts for the copolymerization of an unsaturated alkyd resin with a compound containing the cH,=o V

group.

An object of this invention is to increase the speed of copolymerization between an unsaturated alkyd resin and a substance containing the group in the presence of an organic peroxide and a polyvalent metal in a reduced form as compared to its most oxidized form such as iron or a ferrous salt which may bean inorganic salt, e. g.. ferrous chloride, or an organic salt e. 2., the salt obtained by reacting the half ester of diethylene glycol and maleic acid and powdered iron at about l30-150 C. The proportion of polyvalent metal, such as iron, may be varied widely but, with the proportion of peroxide catalyst ordinarily used, from 0.005% to 0.1% is suitable, although it is preferable that at least 0.02% of the polyvalent metal be used to obtain excellent results. However, should it be desirable to increase the time required for gelation or curing in certain processes, the concentrations of polyvalent metal may be less than 0.02%. The proportion of polyvalent metal should, in general, be based upon theproportion of organic peroxide catalyst employed. It is preferable that the weight ratio of the peroxide to the polyvalent tions are in parts by weight are given by way of illustration and not in limitation.

Preparation of ferrous salt of diethylene glycol monomaleate About 1 mol of diethylene glycol and 1 mol of maleic anhydride are heated at about -150 C. to form the half ester. From 2 to 5% of powdered iron is added to the half ester at a temperature of about C. to form a ferrous salt of diethylene glycol monomaleate.

Example 1 About 1 part of styrene is intimately mixed with 2 parts of an unsaturated alkyd resin, a polyester of 6 mols of diethylene glycol, 5 mols of fumaric acid and 1 mol of sebacic acid, to form a homogeneous mixture. To this mixture is added 0.5% of the iron salt prepared above, which is equivalent to about 0.06% Fe, as a 40% aqueous solution and thoroughly stirred. Upon addition of 0.5% of lauric peroxide a gel results in about 1 minute at about 25 C.

Example 2 Example 3 Example 1 is followed except that 0.2% of the iron salt and 0.2% of lauric peroxide is used. A gel results in about 45-60 minutes at a temperature of 25 0.

Example 4 Example 2 is repeated with the substitution of 0.2% 01 benzoyl peroxide for the lauric peroxide. A gel is obtained in 8-10 minutes at 25 0.

Example 5 The procedure in Example 2- is followed with the exception that 0.2% of benzoyl peroxide is used in place of the lauric peroxide. A gel is obtained in about 45-60 minutes at 25 0.

Example 6 Example 1 is followed with the exception that a 0.2% of lauric peroxide and 0.25% of the iron salt dissolved in ethylene glycol are used. A gel results in 3 to 5 minutes at a temperature of 25 0.

Example 7 About 1 part of styrene is intimately mixed with 2 parts of an alkyd resin (a diethylene glycol fumarate modified with sebacic acid as described in Example 1) to form a homogeneous mixture.

Oflfi lauric peroxide 3 is incorporated in the mixtureand 0.021% oil'e. as non dissolved in ethyleneliycol, isaddcdat about25' C. Themixture gels in about 1 minute at 25' C. and is fully cured aiteraboutmminutes.

Example 8 Ixampie 7 is except'that the'iron ooncaitration is lowered toil.0l%. This gels in 45 minutaaat25'0.andcuresin135minutes atthe sametemperature.

Example 9 lxample'lisrepeatedwiththeuceptionthat uwiiiciironisemploycd. Thisresultsina sel inthoursatatemperatureoififfiandisiuily curcdinMhours.

'Amoi'thepolyvaientmetalsorsaltsthereoiwherethemetalisinareducediormascomparcd toitsmostoxidiaedstatemaybeusedinaccordance with myinvention. Preferably salts of the polyvaientmetalsareusedandtheyaredesirabiyintroduced into the copolymerizable mixtures inlthe form of solutions in organic solvents such 4 formed the resin is preierabiy iuily cured by heating at elevated temperatures of 70-110 0.

Coatings 01 my resinous mixtures containing a polyvalentmetalmaybegeliedtherebysothat pressureandheatmaybeapfliedtocmethereoinouscoatimandthelatterdoesnotaoueeae outbuthassuiiicientbodythataiiimoisubstantialthicknessremainsinplace.

Temperatures oi M C. are satisfactory for curing castings or thick articles when a polyvalentmetalisusedinaccordancewithmyinvention. However, if desired, higher or lower p rahn s ybeemployedandinorderio aroupwhichareparticuhrlyuaeiulinmyinvem as, ethylene glycol, diethylene glycol, acetone,

dioaane, etc. The salts may be anhydrous or hydrated such as SliClaZHaO.

' It will be apparent from a consideration of my examples that I am able to obtain fast curing compositions which may be cast at ordinary room temperatures. Previouslyit' has been customary to employ much, higher temperatures for curing resins oi the type employed herein in order to obtain cured products quickly. My invention thereiore makes it possible to produce castings or other articles without the use of expensive ovens or other means of supplying heat to the polymerizing compositions while they are being cured. Furthermore at relatively high temperatures large castings or laminates, that is those with thick sections often crack or blister whereas when low curing temperatures are employed flawless products are obtained; Here again my invention overcomes, this diiiiculty since at the low tem-' peratures which may be used in accordance with my invention-thick articles may be produced satisiactorily. 7

My invention is particularly adapted for use in the production of castings but it may also be used in the production of laminated materials, moldings, etc. 'One advantageous application of my invention is in the use of my resin mixtures containing a polyvalent metal to impregnate cloth to be used iniaminating. The polyvalent metaicauses the resin to set and the impregnated cloth may then be drawn in forming a iaminate in a complex shape. After the laminate is tlonarethosewhichhave'aboiling pointoiat leastiio'qandarethereiorenormailyliquid. Furthermore, thesesubatances do not contain con g ted carbon-to-carbon double bonds since thesecompoundsareknowntoreactwiththemselvesorwithothercompoimdssuchasmaleic esters bya 13-1,! additionmechanism commonly knownastheDiels-Aiderreaction.

Onthe other handcompoundssuch asthose in accordance with the present invention and which contain noconjuxated carbon-to-carbon double bonds obviously cannot undergo this p of reaction withthe maieic esters. Accordingly, my invention is not directed to the use of unsaturated compoimds containing coni l ted systems of carbon-tc-carba double bonds. llany substances which contain carbon-to-carbon double bonds conills ted with respect to oxygen are suitable for use according to this invention since they do not react with unsaturated alkyd resins in an undesirable manner but instead copoiymerize or interpoiymeriae to form substantially insoluble resins. I

Theunsaturated alkyd resins which are suitable for use in accordance with my invention are those which are polyesters of an alpha, beta unsaturated polycarboaylic acid and a polyhydric alcohol. The unsaturated alkyd resins may be modified with monohydric alcohols or monocarboxylic acids. However, the proportions of the varioussuhstancesesteriiiedtoiormtheresin are suchthatthepolyesterisformediromsubstancs having a total of about one hydroxyl Iroup [or each carboxyl group.

Among the alpha, beta unsaturated polycarboxylic acids which may be used some examples are maleic acid, iumaric acid, itaconic acid, citraconic acid, etc. Mixtures of alpha, beta polycarboxylic acids maybe used, and mixtures of polycarboxylic acids including one or more alpha, beta unsaturated polycarboxylic acids and a saturated aliphatic polycarboxylic acid or an aromatic polycarboxylic acid may be employed. In some cases, particularly when the unsaturated alkyd resin is to be used for copolymerization with styrene or other aromatic vinyl hydrocarbons it is desirable that the unsaturated alkyd resin contain a small proportion of a relatively long chain polycarboxylic acid such as adipic acid or sebacic acid, or of an aromatic polycarboxylic acid such as phthalic acid or endomethylene tetrahydrophthalic anhydride.

' tain paper or fabric composed of cellulose fibers,

The term acid as used herein, is intended to cover the anhydride as well as the acid since the anhydride may be used'whenever available and desirable.

The unsaturated alkyd resins are preferably polyesters of glycols, but other polyhydric alcohols including glycerine, pentaerythritol, dipentaerythritol, polyallyl alcohol etc., may be used. Examples of glycols which maybe employed are ethylene glycol, diethylene glycol, trimethylene glycol, alpha-propylene glycol, any of the butylene glycols, decamethylene glycol, octadecandiol etc.

Among the monocarboxylic acids which may be employed as modifiers some examples are acetic acid, caproic acid, lauric acid, myristic acid, stearic acid, oleic acid, linoleic acid, linolenic acid etc. Some examples of the monohydric alcohols which may be used as modifiers are n-butanol, propanol, isopropanol, the amyl alcohols, cyclohexanol, 2-ethyl hexanol, dodecanol, cetyl alcohol, octadecanol, benzyl alcohol, furfuryl alcohol and tetrahydroabietyl alcohol, etc.

When glycols are reacted with a dicarboxylic acid it is preferable that the glycol be present in a molal ratio to the acid of not less than .1 :2 and the molal ratio of monohydric alcohol to dicarboxylic acid not greater than 1:1. In most cases the molal ratio of monohydric alcohol to dicarboxylic acid of about 1:6 produces the best results (5.5 mols of glycol being employed in this case). The proportion of monocarboxylic acid which may be used should similarly be less than 1:2 in most instances. If a dicarboxylic acid which does not contain an alpha, beta unsaturation is used to modify the unsaturated alkyd resins it is preferable that the molal ratio thereof to the alpha, beta unsaturated polycarboxylic acid be less than about 1:2 and preferable that the ratio be about 1:5.

The unsaturated alkyd resins are produced in accordance with technique well known in the alkyd resin art. The final product should preferably have an acid number not greater than 50, although in some cases resins having an acid number as high as 100 niay be desirable.

Some of the peroxides which may be employed as catalysts in accordance with the present invention in conj ction with the polyvalent metal such as a ferrous salt are: benzoyl peroxide, phthalic peroxide, succinic peroxide, benzoyl acetic peroxide, fatty oil acid peroxides, alcohol peroxides e. g. tertiary butyl hydroperoxide and glass fibers, asbestos fibers, synthetic fibers etc.

In my copending application Serial No. 558,087, filed Oct. 10, 1944 entitled Acceleration of the cure of copolymers I have described and claimed the use of stannous salts for the accelerating or modifying the cure of copolymerizable mixtures as described herein.

Obviously many modifications and variations may be made in the compositions and processes described herein without departing from the spirit and scope of the invention as defined in the appended claims.

I claim: 7

1. A process which comprises copolymerizing in bulk a homogeneous mixture including a polymerizable liquid substance containing the group which has no'carbon-to-carbon conjugation, an unsaturated alkyd resin obtained by esterifying a mixture including a po yhydric alcohol and an alpha, beta-unsaturated polycarboxylic acid and about 0.1 -5% of an organic peroxide catalyst in the presence of a ferrous salt selected from the group consisting of ferrous chloride and the ferrous salt of diethylene glycol monomaleate, the weight ratio of the peroxide to the ferrous salt being between about 25:1 and 2:1 (based on the metal), said ferrous salt being the sole activator of said peroxide catalyst present .in said homogeneous mixture.

2. A process as in claim 1 wherein the ferrous salt is ferrous chloride, and wherein the temperature of polymerization is about 20-30 C.

3. A process as in claim 1 wherein the ferrous REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Date Number Name I 2,305,224 Patterson Dec. 15, 1942 2,344,875 Owens et al Mar. 21, 1944 2,370,010 Clifiord et al. Feb. 20, 1945 2,380,473 Stewart (1) July 31, 1945 2,380,474 Stewart (2) July 31, 1945 

